1 Applications

1.1 Preprocessors

DrIFT is a tool which allows derivation of instances for classes that aren't supported by the standard compilers. In addition, instances can be produced in seperate modules to that containing the type declaration. This allows instances to be derived for a type after the original module has been compiled. As a bonus, simple utility functions can also be produced from a type.

Strafunski is a Haskell bundle that provides support for generic programming in Haskell, based on the concept of a functional strategy. It consists of a combinator library (StrategyLib) and a precompiler (DrIFT-Strafunski).

A program using Template Haskell must link with the TH library even if it contains no references to TH after it has been compiled. Zeroth is a preprocessor which allows modules to use TH without linking with the TH library. To do this, Zeroth evaluates the top level splices from a module and saves the resulting code.

1.2 Build systems

The Haskell Cabal is a Common Architecture for Building Applications and Libraries. It is an API distributed with GHC, NHC98, and Hugs which allows a developer to easily group together a set of modules into a package. It is the standard build system for new Haskell libraries and applications

1.3 Source tags

Hasktags is a simple program that generates TAGS files for Haskell code. Together with a supporting editor (e.g. NEdit, XEmacs, or Vim) TAGS files can be used to quickly find the places where functions, data constructors etc. are defined.

HotHaskTags is a reimplementation of HaskTags that is more aware of the structure of Haskell source. If you have multiple functions of the same name in a project and jump from a file, it will analyze the imports of that file (including qualified imports correctly) and jump to the one that is being referred to. Extended ctags format only (read: Vim only).

Another reimplementation of hasktags which has a better understanding (than hasktags) of Haskell syntax. ctags files are generated in the traditional format only; where the same identifier is reused, gasbag attempts to determine the best one for inclusion in the ctags file.

1.4 Program Transformation

Mechanical refactoring of Haskell code (across module boundaries). HaRe now supports many refactorings such as renaming identifiers, moving/introducing/inlining definitions, and so on. Those refactorings are not limited to a single module. HaRe can be accessed from either Vim or Emacs

This Haskell utility takes a program implemented in multiple modules and converts it to a single module. This way you get whole program optimization for compilers that do not support that. Resulting programs will be probably faster using this method.

Tool for deriving hylomorphisms from a restricted Haskell syntax. It is based on the algorithm first presented in the paper "Deriving Structural Hylomorphisms From Recursive Definitions" at ICFP'96 by Hu, Iwasaki, and Takeichi.

1.5 Documentation and browsing

A tool for automatically generating documentation from annotated Haskell source code. It is primarily intended for documenting libraries, but it should be useful for any kind of Haskell code. Haddock lets you write documentation annotations next to the definitions of functions and types in the source code, in a syntax that is easy on the eye when writing the source code (no heavyweight mark-up). The documentation generated by Haddock is fully hyperlinked - click on a type name in a type signature to go straight to the definition, and documentation, for that type.

IDoc extracts interface documentation and declarations from Haskell modules based on standard Haskell layout rules and a small number of clues that the programmer embeds in interface comments. These clues have been designed to be visually non-imposing when displaying the source in a text editor. Interface documentation is rendered in standard markup languages (currently, only HTML is supported). IDoc has been designed to be simple to use and install.

This program generates an HTML document showing the module interfaces of a Haskell project. Convenient links are placed for easy browsing of the different modules of the project, and for quick access to the source code.

HaSpell is a spelling and style checker for Haskell programs. It can detect spelling errors in comments in the program text, and optionally in the code itself. There is an option to detect metasyntactic variables (such as 'foo') and 'bad function prefixes' such as 'compute' and 'doThe' - these make the program less readable and generally indicate bad programming style.

Lambdabot is a large, ad-hoc collection of Haskell development tools available for offline use. In particular, automatic point-free refactoring is available via a vim interface, as well as access to Hoogle, djinn, ghci, and much much more.

1.6 Tracing & debugging

Tracing gives access to otherwise invisible information about a computation. Conventional debuggers allow the user to step through the program computation, stop at given points and examine variable contents. This tracing method is quite unsuitable for Haskell, because its evaluation order is complex, function arguments are usually unwieldy large unevaluated expressions and generally
computation details do not match the user's high-level view of functions mapping values to values.

Buddha is a declarative debugger for Haskell 98 programs. It presents the evaluation of a Haskell program as a series of function applications. A typical debugging session involves a series of questions and answers. The questions are posed by the debugger, and the answers are provided by the user. The implementation of Buddha is based on program transformation.

A compiler for a subset of Haskell. Running a compiled program creates an evaluation dependency tree as trace, a structure based on the idea of declarative debugging from the logic programming community. A debugging session consists of the user answering a sequence of yes/no questions.

A Haskell program is first transformed by hat-trans and then compiled with nhc98 or ghc. At runtime the program writes a trace file. There are tools for viewing the trace in various ways: Hat-stack shows a virtual stack of redexes. Hat-observe shows top-level functions in the style of Hood. Hat-trail enables exploring a computation backwards, starting from (part of) a faulty output or an error message. Hat-detect provides algorithmic debugging in the style of Freja. Hat-explore allows free navigation through a computation similar to traditional debuggers and algorithmic debugging and slicing.

A library that permits to observe data structures at given program points. It can basically be used like print statements in imperative languages, but the lazy evaluation order is not affected and functions can be observed as well.

Another tool helping literate programming in Haskell. It helps to maintain views in a literate programming project. For example, it is among the tools used for developing a compiler in an iterative way with manuals didactically reflecting these evolving series of versions deriving from the literal code (see Essential Haskell Compiler project). Thus, Shuffle gives us the possibility for making didactically the evolution of versions visible in the documentation, when this is needed. More generally, Shuffle gives us tangling and weaving possibilities of literate programming. I think it gives a way to think of literal program development in a more abstract way by supporting the concept of views (maybe a too far analogy: version control management -- e.g. darcs -- helps thinking of program development in a more abstract way, too). Shuffle works well together with lhs2tex.

Ian Lynagh's Haskell2LaTeX takes a literate Haskell program, or any LaTeX document with embedded Haskell, and pretty-prints the Haskell sections within it. The most significant difference between Haskell2LaTeX and other programs with similar goals is is that Haskell2LaTeX parses the input rather than merely lexing it.

1.10.1 TeX

A TeX package for typesetting literate scripts in TeX. The output looks much like the code from Chris Okasaki's book "Purely Functional Data Structures", doing syntax highlighting and converting ASCII art such as -> or alpha to proper mathematical symbols. It should work with both LaTeX and plain TeX, and it does its magic without any annotations, directly on the source code (lambdaTeX uses an almost-complete Haskell lexical analyzer written entirely in plain TeX). You only have to add \input lambdaTeX at the top of your source file, and manually typeset your literate comments so they look as good as the source code.

2 Editor support

2.1 Integrated Development Environments

Visual Haskell is a complete development environment for Haskell software, based on Microsoft's Microsoft Visual Studio platform. Visual Haskell integrates with the Visual Studio editor to provide interactive features to aid Haskell development, and it enables the construction of projects consisting of multiple Haskell modules, using the Cabal building/packaging infrastructure.

Eclipse is an open, extensible IDE platform for "everything and nothing in particular". It is implemented in Java and runs on several platforms. The Java IDE built on top of it has already become very popular among Java developers. The Haskell tools extend it to support editing (syntax coloring, code assist), compiling, and running Haskell programs from within the IDE. More features like source code navigation, module browsing etc. will be added in the future.

Leksah is an IDE for Haskell written in Haskell. Leksah is intended as a practical tool to support the Haskell development process. It is an pre-release phase with bugs and open ends but actively developed and moving quickly. Hopefully, Leksah will already be interesting, useful and fun. Leksah uses GTK+ as GUI Toolkit with the gtk2hs binding. It is platform independent and should run on any platform where GTK+, gtk2hs and GHC can be installed. I have tested it on Windows and Linux. It only supports GHC.

Through the dark ages many a programmer has longed for the ultimate tool. In response to this most unnerving craving, of which we ourselves have had maybe more than our fair share, the dynamic trio of #Haskellaniacs (dons, dcoutts and Lemmih) hereby announce, to the relief of the community, that a fetus has been conceived: hIDE - the Haskell Integrated Development Environment. So far the unborn integrates source code recognition and a chameleon editor, resenting these in a snappy gtk2 environment. Although no seer has yet predicted the date of birth of our hIDEous creature, we hope that the mere knowledge of its existence will spread peace of mind throughout the community as oil on troubled waters. See also: HIDE/Screenshots of HIDE and HIDE

Vital is a visual programming environment. It is particularly intended for supporting the open-ended, incremental style of development often preferred by end users (engineers, scientists, analysts, etc.).

Pivotal 0.025 is an early prototype of a Vital-like environment for Haskell. Unlike Vital, however, Pivotal is implemented entirely in Haskell. The implementation is based on the use of the hs-plugins library to allow dynamic compilation and evaluation of Haskell expressions together with the gtk2hs library for implementing the GUI.

Haskell Mode for Emacs supports font locking, declaration scanning, documentation of types, indentation and interaction with Hugs/GHCi. See the Haskell mode for Emacs wiki page for setup and usage tips, including how to get the CVS version. XEmacs users should also check out the minor bugs noted in that page.

2.2.1 Other

3 Libraries

3.1 Testing

A unit testing framework for Haskell, similar to JUnit for Java. With HUnit, the programmer can easily create tests, name them, group them into suites, and execute them, with the framework checking the results automatically. Test specification is concise, flexible, and convenient.

A tool for testing Haskell programs automatically. The programmer provides a specification of the program, in the form of properties which functions should satisfy, and QuickCheck then tests that the properties hold in a large number of randomly generated cases. Specifications are expressed in Haskell, using combinators defined in the QuickCheck library. QuickCheck provides combinators to define properties, observe the distribution of test data, and define test data generators.

The HTF lets you write HUnit tests and QuickCheck properties in an easy and convenient way. Additionally, the HTF provides a facility for testing programs by running them and comparing the actual output with the expected output (so called "file-based tests"). The HTF uses Template Haskell to collect all tests and properties, so you do not need to write boilerplate code for that purpose. Preprocessor macros provide you with file name and line number information for tests and properties that failed.

Hpc is a tool-kit to record and display Haskell program coverage. Hpc includes tools that instrument Haskell programs to record program coverage, run instrumented programs, and display the coverage information obtained.

Functional programmers often appeal to equational reasoning to justify various decisions made in both design and implementation. This page introduces the Haskell Equational Reasoning Assistant (HERA), an architecture that provides both a GUI level and a batch level Haskell rewrite engine inside a single tool.

pqc provides Test.QuickCheck.Parallel, a QuickCheck driver that runs jobs in parallel, and will utilise as many cores as you wish, with the SMP parallel GHC 6.6 runtime. It is simple, scalable replacement for Test.QuickCheck.Batch.

Two libraries for GHC. The first is for printing heap objects from within Haskell or C code. The second is for dumping the contents of the Stable Table which is used for Stable Pointers and Stable Names.